The hypothesis that non-shivering thermogenesis (NST), mediated by brown adipose tissue mitochondria (BATM), is linked to obesity and the regulation of body weight has been recently proposed. The molecular basis for this weight regulating ability is an occurrence of a nucleotide binding protein (NbP) within the BATM inner membrane which imparts the unique capability of controlled uncoupling of respiration from normal regulatory mechanisms, thus permitting loss of energy as heat. The metabolic regulation of the NbP, and thus NST, has not been ascertained. It is known that purine nucleotides will bind and inhibit the function of the NbP, however, no activator of the NbP function has been clearly established. The NbP has many physical similarities to the adenine nucleotide translocase (ANT), which is regulated by long chain acyl CoA thioesters. It is our hypothesis that these ligands may act in a similar fashion with the NbP. This investigation will first attempt to reconstitute the purified NbP from cold adapted hamsters and use this model to characterize the effect long chain acyl CoA's have as potential metabolic regulators. The second objective will be the study of regulatory ligand interactions with NbP isolated from the genetically obese, ob/ob mouse. The characterization of NbP regulation in the ob/ob mouse has implications in the study of human obesity as these rodents have a defective NST capacity although total NbP quantity remains unchanged. Thirdly, the BAT and subcellular fraction concentration of long chain acyl CoA's will be analyzed by high pressure liquid chromatography to determine at what potential concentrations these ligands could be acting.